DESCRIPTION (Investigator's Abstract): This proposal uses psychophysical methods to examine human binocular vision and motion perception, with particular emphasis on interactions among the neural mechanisms underlying these aspects of vision. In some cases, experimental work is derived from theories of stereopsis and structure from motion. Specific questions to be addressed include: a) the coexistence of stereopsis and binocular rivalry; b) the locus of binocular suppression relative to the analysis of motion information and the site of covert visual attention; c) interactions between stereopsis and kinetic depth in specifying structure from motion; d) motion perception and stereopsis in patients with Alzheimer's disease. Specific methods include forced-choice measurement of: stereoscopic discrimination performance (questions a.c and d), reaction time using a cued location paradigm (question b), motion aftereffect duration and/or strength following adaptation to complex motion (question b) and minimum motion signal necessary to perceive coherent motion (question d). Results from these experiments, besides providing information on the nature and sequence of processing underlying binocular vision and motion perception, may provide important clues concerning the perceptual consequences of neural dysfunctions underlying Alzheimer's disease.